Google Gson Linkedtreemap Class Cast to Myclass

google gson LinkedTreeMap class cast to myclass

Serializing and Deserializing Generic Types

When you call toJson(obj), Gson calls obj.getClass() to get information on the fields to serialize. Similarly, you can typically pass MyClass.class object in the fromJson(json, MyClass.class) method. This works fine if the object is a non-generic type. However, if the object is of a generic type, then the Generic type information is lost because of Java Type Erasure. Here is an example illustrating the point:

class Foo<T> {  T value;}
Gson gson = new Gson();
Foo<Bar> foo = new Foo<Bar>();
gson.toJson(foo); // May not serialize foo.value correctly
gson.fromJson(json, foo.getClass()); // Fails to deserialize foo.value as Bar

The above code fails to interpret value as type Bar because Gson invokes list.getClass() to get its class information, but this method returns a raw class, Foo.class. This means that Gson has no way of knowing that this is an object of type Foo, and not just plain Foo.

You can solve this problem by specifying the correct parameterized type for your generic type. You can do this by using the TypeToken class.

Type fooType = new TypeToken<Foo<Bar>>() {}.getType();    
gson.toJson(foo, fooType);
gson.fromJson(json, fooType);

I have Parent class and it's child class some of them having List types in it. Like this parent class i have 30 files. I solved it like this.

Gson gson = new Gson();
JSONObject jsonObj = new JSONObject(object.get(DO_SERVICES).toString());
Type type = new TypeToken<MyDto>() {}.getType();
servDto = gson.fromJson(jsonObj.toString(),type);

The most important thing is, I can't reproduce this error in local testing from Android studio. This problem pops up only, When i generate signed apk and publish app into PlayStore were the app stops, and the report says Cannot cast LinkedTreeMap to myclass.

It was hard for me to reproduce the same result in my local testing (includes Debug mode).

class com.google.gson.internal.LinkedTreeMap cannot be cast to class Return

This is caused by type erasure on the JVM: at runtime, the function getObject doesn't know what type T is. You need to make it an inline function and use a reified type. Change it as follows and it should work:

inline fun <reified T> getObject(url: String): T {
    ... leave body as before
}

class com.google.gson.internal.LinkedTreeMap cannot be cast to class Partner

It is due to type erasure in runtime. In Kotlin you can solve this issue by making your function inline with reified type:

Change your function from:

fun <T> fromJson(json: String?): T {
    return Gson().fromJson<T>(json, object: TypeToken<T>(){}.type)
}

To:

inline fun <reified T> fromJson(json: String?): T {
    return Gson().fromJson<T>(json, object: TypeToken<T>(){}.type)
}

For further reading check this out: https://kotlinlang.org/docs/reference/inline-functions.html

com.google.gson.internal.LinkedTreeMap cannot be cast

You are using ArrayList<ListPojo> so you need to make sure that the parsing should happen using right type List<ListPojo> instead of list which has no type

due to the missing type information , gson is returning a List of internally
created objects LinkedTreeMap and since you are using raw types (should be a warning for unchecked cast)with declaration as concrete type which will create a issue when adapter actually expecting a PojoObject but internally it's something else. so solution

Never use raw-types anywhere possible

so do

public interface CountryArrayAPI {
    @GET("api/popular_destinations")
    public Call<List<ListPojo>> getCountries();
}

and also remove / before api and call will be like

call.enqueue(new Callback<List<ListPojo>>() {

            @Override
            public void onResponse(Call<List<ListPojo>> call, Response<List<ListPojo>> response) {
            listPojos = response.body();

and always code to interface so

List<ListPojo> listPojos = ...;

How to deal with cannot be cast to class error - GSON JAVA

public List<Medicine> FromJsonToArray() throws IOException {
    String medicineJson = initArray("Medicines.json").toString();
    Gson gson = new Gson();
    Type medicineListType = new TypeToken<List<Medicine>>() {}.getType();
    List<Medicine> medicineArray = gson.fromJson(medicineJson, medicineListType);
    return medicineArray;
}

should do the trick.

Basically it is a workaround to tell gson to deserialize to a list of particular class.

That is required because generics are lost at runtime and your json was being deserialized to List<LinkedTreeMap> instead of List<Medicine>.

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